This application relates generally to the identification of turbulence. More particularly, this application relates to the identification of turbulence by analysis of convective cells detected by aircraft hazard warning systems.
Hazardous weather is generally associated with convective weather cells. Convective weather cells can produce turbulence, high winds, lightning, hail, and other weather hazards. With the large amount of air traffic and rising fuel costs, pilots are interested in identifying convective cells (e.g., often hazardous weather) from non-convective cells (e.g., stratiform rain) so they do not unnecessarily avoid flight routes through non-hazardous weather. Convective cells can also provide dangerous and uncomfortable flight conditions for the crew and passengers.
Lightning is generally caused when mixed state hydrometeors rub together in vertical shearing regions inside convective cells. Generally, cells that are producing lightning are turbulent and have the capacity to produce hail. Therefore, the presence of lightning in a particular area can be an indication of the presence of a convective cell or at least a potentially hazardous weather region.
Weather radar systems generally include an antenna, a receiver/transmitter circuit, a processor, and display. The processor is coupled between the display and the receiver/transmitter circuit. The receiver/transmitter circuit is coupled between the processor and the antenna. The processor provides transmit signals through the receiver/transmitter circuit to the antenna to transmit radar beams. The processor receives radar return signals derived from radar returns received by the antenna. The radar return signals are provided to the processor via the receiver/transmitter circuit.
Conventionally, pilots use weather radar systems to detect and avoid hazardous weather. The radar return signals are processed to provide graphical images to a radar display. The radar display is typically a color display providing graphical images in color to represent the severity of weather. Some aircraft systems also include other hazard warning systems such as a turbulence detection system. The turbulence detection system can provide indications of the presence of turbulence or other hazards.
Conventional aircraft hazard weather radar systems, such as the WXR 2100 MultiScan™ radar system manufactured by Rockwell Collins, Inc., have Doppler capabilities and are capable of detecting four parameters: weather range, weather reflectivity, weather velocity, and weather spectral width or velocity variation. The weather reflectivity is typically scaled to green, yellow, and red color levels that are related to rainfall rate. The radar-detected radial velocity variation can be scaled to a turbulence level and displayed as magenta.
Although radar-detected reflectivity and radar-detected velocity variation are correlated to aircraft hazards, they may not provide a complete picture to the pilot. For example, rainfall rates derived from radar reflectivity data are generally related to the most visible weather related advisory on the flight deck. However, heavy rain is not inherently hazardous to the aircraft. Heavy rain is displayed to the flight crew because it is often associated with true weather hazards such as lightning, hail, and turbulence.
Some weather radar systems incorporate turbulence detection functions. In areas of reasonably high reflectivity, conventional aircraft hazard warning systems can detect variation in the velocity signatures within thunderstorms. This velocity variation, or spectral width in radar terminology, is correlated to turbulence within the storm. Conventional turbulence detection algorithms have limitations, however. Direct radar based turbulence detection systems typically have a short range, for example up to about forty or fifty nautical miles. Forty nautical miles is a relatively short distance when air crews are trying to maneuver near storm cells. In addition, turbulence thresholds are typically set so high to adhere to regulatory agencies that the turbulence is only visible in the cores of convective cells, areas which aircrews avoid anyway due to very high (red) reflectivity. A conventional turbulence detector has generally been incapable of adjusting with respect to geographic location.
Thus, there is a need for a system and method for more accurate, long range detection of turbulence. There is also a need for inferring the existence of turbulence based on the detection and analysis of convective cells or hazards associated therewith. There is also a need to detect and locate turbulent weather cells as opposed to non-turbulent, isolated cells. Further still, there is a need to detect and locate turbulent convective cells as opposed to non-turbulent convective cells. Yet further, there is a need for a aircraft hazard warning system optimized to determine the location and presence of turbulent cells. Further, there is a need for a aircraft hazard warning system that includes more functions than a conventional rain gauge.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.